This invention relates to imaging apparatus and methods.
An imaging apparatus that performs imaging and focus detection by using an image sensor, in which focus detection pixels used in a pupil-division type phase difference detection method are arranged amongst the two-dimensionally-arranged imaging pixels, is known, for example, from Japanese Laid-Open Patent Publication No. 2000-305010. In such an imaging apparatus, data of imaging pixels at positions of the focus detection pixels, that is, the pixel data output from the imaging pixels disposed at the proper positions of the focus detection pixels, is determined by averaging the pixel data of the imaging pixels around the proper focus detection pixels.
However, with the pixel data determined by a pixel compensation process using such averaging, there is a problem in that the image quality decreases as the spatial frequency of the image becomes closer to the Nyquist frequency which is related to an image pitch of the image.
For example, for an image with black-and-white vertical stripes, in which the spatial frequency is equal to the Nyquist frequency, if the pixel data at the positions of the focus detection pixels is compensated by averaging the pixel data of the imaging pixels that are adjacent diagonally in four directions from the focus detection pixels, the white and the black are inversely imaged in the proper data and in the compensated data.
This occurs because, by inserting a focus detection pixel array between the imaging pixel arrays, the pitch of the imaging pixels becomes larger in the proximity of the focus detection pixel array, and accordingly, the Nyquist frequency of the image is changed to a low frequency, thereby reducing the reproducibility of images.
In particular, if the focus detection pixels or defective pixels are arranged linearly, and if an image having a high spatial frequency component exists in the direction perpendicular to the direction of such an arrangement, image deterioration becomes easily visibly noticeable when compensating the pixels by the above-described averaging process.